The potato is a tuber -- the iris (bearded and most beardless) is a rhizome. The two plant structures have some similarities, but quite a few differences in composition and structure, so the two cannot be compared.
grannysgarden said:Interesting Lee-Roy. Then some of my bloom outs may start some regrowth. 
that is true, if the mother rhizome has active sets of live plant tissue in addition to the increases on either side of the bloom stalk. I have always allowed a bloom out to stay in place for another year, at least. About 60-70% of the time, i'll see new set of shoot(s) many time those resurgent new increases will come at the "toe" of the old rhizome, and some towards the middle of the old rhizome.
Additional evidence that i've seen, for persistent live groups of plant tissue on the old rhizome, is from my battle with wintertime botrytis -- (which i've won, for the record). The malady will completely destroy the above ground rhizome but new increases will show up the follow spring from locations nowhere near the usual spots near last years bloom stalk. Digging down a bit i discovered new live shoots from the middle to even the bottom side of the old rhizome. I also found new growth from new tiny round marble like rhizomes that i didn't even know were developing.
One thing i didn't mention, from my initial observation post in this thread, is the varieties that were rapid increasers tended to have more active site along each side of the rhizome for shoots to appear. Cultivars who had a slower rate of increase ive had more of a failure rate trying to get new shoots to appear. So trying to re-cultivate old mother rhizomes for increase is hit or miss depending on the variety.
